Figure 1 shows the grade block model (vertical cross-section) of a porphyry copper deposit. The grades of copper (%Cu) are shown in the section and additional information provided for this mining project as below: Copper price Sales cost Mining cost Milling cost . Mill recovery Overall slope angle of the pit Block volume LI Rock density 2.5 tonne per cubic meter Assume the mining cost increases by $0.1 for each lower level (just for calculation of block economic values, not for the breakeven cut-off grade). L2 L3 0 L4 0 0.1 0.1 0 0.39 0.35 0.1 0.3 0 0.4 = $5,500/tonne of copper = $500/tonne of copper $2.0/tonne of rock $10.0/tonne of ore 95% = 45 degrees (IH:1V) =1000 cubic meter 0.1 0.2 0.3 0.3 0 0.1 Based on this information answer the following questions: 0 0.45 0.2 0.1 0.42 0.5 Figure 1: Vertical cross-section through the ore body showing block grades (%Cu) 0 0.2 0 0.1 0 a. [Marks=3] Calculate the breakeven cut-off grade. b. [Marks = 4] Considering the calculated breakeven cut-off grade, calculate the block economic values ('000$/tonne). c. [Marks = 8] Determine the optimum ultimate pit outline by using Lerchs-Grossmann (LG) 2-D Algorithm and report the pit outline value. Note: show all steps. d. [Marks = 8] If the mining capacity is 10 blocks per year and the processing capacity is 3 blocks per year, work out the best way (pushbacks) to mine this deposit and the corresponding production schedule, assuming no stockpile. Compare the answers with the strategy of mining bench-by-bench. e. [Marks=2] What is the Overall Stripping Ratio for this section as shown in Figure 1? Figure 1 shows the grade block model (vertical cross-section) of a porphyry copper deposit. The grades of copper (%Cu) are shown in the section and additional information provided for this mining project as below: Copper price Sales cost Mining cost Milling cost . Mill recovery Overall slope angle of the pit Block volume LI Rock density 2.5 tonne per cubic meter Assume the mining cost increases by $0.1 for each lower level (just for calculation of block economic values, not for the breakeven cut-off grade). L2 L3 0 L4 0 0.1 0.1 0 0.39 0.35 0.1 0.3 0 0.4 = $5,500/tonne of copper = $500/tonne of copper $2.0/tonne of rock $10.0/tonne of ore 95% = 45 degrees (IH:1V) =1000 cubic meter 0.1 0.2 0.3 0.3 0 0.1 Based on this information answer the following questions: 0 0.45 0.2 0.1 0.42 0.5 Figure 1: Vertical cross-section through the ore body showing block grades (%Cu) 0 0.2 0 0.1 0 a. [Marks=3] Calculate the breakeven cut-off grade. b. [Marks = 4] Considering the calculated breakeven cut-off grade, calculate the block economic values ('000$/tonne). c. [Marks = 8] Determine the optimum ultimate pit outline by using Lerchs-Grossmann (LG) 2-D Algorithm and report the pit outline value. Note: show all steps. d. [Marks = 8] If the mining capacity is 10 blocks per year and the processing capacity is 3 blocks per year, work out the best way (pushbacks) to mine this deposit and the corresponding production schedule, assuming no stockpile. Compare the answers with the strategy of mining bench-by-bench. e. [Marks=2] What is the Overall Stripping Ratio for this section as shown in Figure 1
